Ignition apparatus



IGNITION APPARATUS Filed July 4, 1944 H T TORNEY Patented Feb. 8, 1949 IGNITION APPARATUS Morgan G. Weatherly, Mount Upton, N. Y., as-

signor to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application July 4, 1944, Serial No. 543,476

16 Claims. 1

This invention relates to ignition apparatus for internal combustion engines, or the like, and more particularly to a radio shielded spark plug and transformer coil unit adapted for use in an ignition system.

One o1" the objects of the present invention is to provide a novel simpliiied unit wherein a high frequency transformer coil is mounted in and electrically connected with a radio shielded spark plug.

Another object is to provide a small compact unit of the above character which is durable and reliable in operation.

Still another object is to provide a novel ignition coil which is adapted to withstand the high temperatures which exist in the shielding barrel of a radio shielded spark plug during engine operation.

A further object is to provide a novel ignition coil of small size which may be incorporated in a standard shielded spark plug without making material alterations in the structure of the spark plug.

A still further object is to provide a novel unit for use in an ignition system of an internal combustion engine whereby the necessity for radio shielding of high voltage conductors is reduced to a minimum.

Another object is to provide a novel spark plugcoil unit of the above character which is so constructed that the coil unit may be removed and renewed with comparative ease.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawing. It is to be expressly understood, however, that the drawing is for the purpose of illustration only and is not intended to define the limits of the invention, reference for this latter purpose being had primarily to the appended claims.

The single figure illustrated in the drawing is a longitudinal sectional view of one form of device embodying the present invention.

The single embodiment of the invention illustrated in the drawing, by way of example, includes a radio shielded spark plug of the ceramic insulated type now in common use on aircraft and similar engines throughout the World. The particular spark plug shown is more fully disclosed in the copendin-g application of Tullio Tognola, Patent No. 2,453,048, led July 13, 1943. In the form shown, the spark plug per se comprises a tubular metallic shell lll which is externally threaded at H for cooperation with a threaded opening in an engine cylinder (not shown) in the manner well understood in the art. The internal wall of shell l0 is preferably provided with a tapered wall portion l2 for suitable cooperation with other parts in supporting the center electrode assembly in a manner which will more fully appear hereafter. A ground electrode which may be oi any suitable known construction, is secured in the lower or inner end of shell l@ by means of silver solder or any other suitable means.

Ground electrode i3 is in cooperative spark gap relation with the enlarged head portion I4 of a center electrode l5 which constitutes part of the conducting means mounted in the dierential bore E5, il of a ceramic or like insulator i8 for conducting high tension electrical current therethrough. The upper end of spindle I9 of the center electrode l5 may be provided with one or more annular grooves or equivalent deformations which are engaged by a rigid insulating compound or cement 2G whereby the center electrode is held within the bore of insulator I. Embedded in filling material 2G and held thereby within the outer end of enlarged bore l' of the insulator is a metallic terminal plug 2l. For a purpose to hereinafter appear, plug 2l preferably consists o1 magnetic flux conducting metal and, if desired, may be of a laminated construction, although the same is not so shown. The inner adjacent ends of terminal plug 2l and spindle I8 are preferably electrically connected by a ne wire conductor 22 wldch is also embedded in iilling compound 20 which serves to seal the bore of the insulator against the leakage of gases from the engine cylinder.

The above described center electrode assembly oi the spark plug is mounted in shell lli in any suitable known manner so as to prevent the leakage of gases from the engine cylinder between insulation lS and the shell. In the form shown, the mounting oi the center electrode assembly is effected by wedging a sleeve 23 of relatively soft metal such as copper between the insulator i3 and tapered wall l2 in shell lll. If desired, the outer wall of insulator l'S may also be provided with a slight taper which will tend to prevent movement thereof by the pressure of the gases within the engine cylinder. Extending upwardly from shell l0 is a metallic shielding barrel 213 which may be operatively secured to said shell in any suitable manner or integral therewith, as shown. The inner diameter of said barrel is Y Vused today on standard shielded sparl plugs.

Vmeans l5, 2i within insulator lil.

larger than the inner diameter of shell It, thereby forming an internal shoulder 25.

A novelly constructed coil unit is slidably Ymounted in barrel 2d around the above-described center electrode unit and is connected with the conducting means or center electrode l5, 2i in a novel manner without materially increasing the diameter and length of the shielding barrel as In the form shown, the coil unit comprises a rigid insulating member 26 which has a recess-21 in one end thereof for slidably receiving the'upper end of the center electrode assembly. Tightly rltted or otherwise suitably secured withinv recess 2l is a core 2e of magnetic flux conducting material, such'as magnetic steel. The core 28 is preierably a laminated structure. If desired, said laminated core may be supplemented by a tubular metallic core member 2g which, if desired, may be formed of several turns of magnetic sheet metal.V The lower'end of core member 'or sleeve 2li Vis terminated a safe distance from the grounded metallic parts of the spark plug to avoid danger of ashovers and, hence, spark plug failure. Additionally, it is desirable to coat core member 29 with a thin layer of insulation, such as enamel. As pointed out above, the terminal member 2l of the spark plug may be made of magnetic n'ux conducting material and, hence,

' may vserve as a coil core or as a supplement to either or both of the core structures 28 and 29.

Rigid insulating member 26 is preferably provided with external ilanges at opposite ends thereof and the secondary winding St of an ignition coil maybe wound on said member between j said hanges, the high potential layer of the winding being adjacent the surface of the insulating member'or spool. The successive vlayers of the secondary winding may be insulated from one another and the outer layer may have an insulating covering 3i made of any suitable heat resisting insulating material. `One suitable insulating material forvforining these layers of the coil is a woven fabric made of ne glass bers and impregnated with an insulating compound such as silicon.'`

Surrounding secondary Winding 39 is a primary winding 32, Vone end or which may be connected as atV 33 to the low potential end of secondary winding 3e. The same end of the primary lil' 4 i3 and lfl for a purpose well understood in the art.

Surrounding coil 32 is a sleeve il@ of magnetic flux conducting material. Sleeve fill is preferably split in the longitudinal direction on the line of the section of Fig. l, thereby preventing the loss of energy in the form of eddy currents around the coil. Sleeve l serves asa path of magnetic flux around the coil windings, thereby suppleel ed,

` inenting the core structure 2l, 28, 29. Sleeve t preferably insulated from primary winding 3B oy means of a thin layer ci insulation which may be or" the saine character as that used in separating the layers of secondary winding 3S. A similar layer of insulation :il is interposed between sleeve and the inner surface oi barrel 2li, this layer extending from one end of the barrel to the other.

'ii'ienovei coil unit described above may be held in place within barrel 2li with spring 3 under compression by means of a tubular adaptor or closure member d2. This member is provided Y with an external flange which engages a shoulder winding may be connected by means of a lead Sil to a terminal 35 suitably secured, such as by cement, in the upper end of insulating member 25, said lead extending through a radial passage 35 in said insulating member. The other end of the primary winding is grounded through the spark plug shell lil, 2&3 as shown ldiagranlmatically at ill. ln actual practice, it is preferable to attach the grounding wire to the spark plug shell att-3l when the closure -rnember to be hereinafter described is inserted in barrel 2li. The

other or high potential end of secondary winding "it is connected by means of a lead 38 to core 28 which is in turn connected by means of a resilient coil spring to the center electrode conducting Conductor 38 ,relerably extends through an opening in the wall of insulating member 2G and is thereby kept Va sale distance from any grounded part of the plug. when current from a suitable source soa fed through primary winding 32, changes in Y said current will cause current to be induced in @le in barrel 2e and is held in placeby spinning the upper edge of the barrel inwardly into overlapping relation with said flange. The joint between barrel and member ft2 may be made weather tight such as by soldering the same with silver solder. Threads l are provided on the outer surface ofY member d2 for receiving the shielding conduit oi a supply cable which may, in be provided with a terminal adapted to engage terminal 35. The shielded input or supply cable may be of standard well known construction. Either before or after closure member l2 is secured in place, the space around and within the 'above-described coil unit is preferably, but not necessarily, iilled with a suitable insulating compound, such as polymerized Cashew-nut-shell oil, and a drying agent as disclosed in Tognola U, S. Patent llo. 3dB/27. This compound, or other similar compounds, may be injected into the space within barrel 2li in liquid form and caused to set as a solid mass of resilient nonmoldable material. In its liquidV form, the compound may be inserted under pressure after evacuating the plug barrel. Some oi thefllling compound is illustrated in the drawing at 5 but all ci the spaces are not shown as beingfil-lecl since such a showing would tend to Obscure other structural features oi the unit.

There is thus provided a novel spari; plug and ignition coil unit whichgis simple and compact and may be vused in the place of spark plugs ernbodied in engines already designed and built. When the Vnovel unit provided is incorporated in a low voltage distribution ignition system all high voltage leads will be eliminated and, hence, the radio shielding requirements will be reduced to -a minimum. .Lldd-itionally,` the possibilities of ignition failures, especially those caused by flashovers at high altitudes, will be minimized.

Although only aY single embodiment ci the invention is illustrated and described in the accompanying drawings and the foregoing specification, it is to be expressly understood vthat the same is not vlimited thereto. For example, the spark plug portion of the unit may vary widely in construction Yand the type of material employed. Various other changes, particularly in the design and arrangement of .parts illustrated and in 'the com- Y of the invention, reference is hadl primarily tothe appended claims.

What is claimed is: f i

1. In ignition apparatus of the class described, a tubular shell having a tubular shielding barrel extending therefrom, a center electrode assembly including a center electrode and insulating means therefor mounted in said shell and tel'- minating intermediate the ends orsaid barrel,

a transformer coilrunit in said barrel, said unit l comprising a spool of rigid insulating material. havingl external flanges at opposite ends thereof and an axial recess in one end thereof for receiving the end of said assembly, a laminated core of magnetic material nlling the inner end of said recess, a secondary winding on said spool between said flanges, a primary winding on said.- secondary winding, a split sleeve of magnetic material around said windings, an insulating sleeve surrounding said sleeve, means for grounding said windings, means extending through the wall of said spool for connecting said secondary winding to said core, resilient means for electrically connecting said core and electrode when said unit is inserted into said'barrel, a terminal in the end of said spool opposite said recess, means connecting said primary winding to said terminal, means secured in the open end of said barrel for holding said unit in said barrel, and insulating means iiliing the spaces in said barrel around said unit and assembly.

2. In ignition apparatus of the class described, a tubular shell having a tubular shielding barrel extending therefrom, a center electrode assembly including a center electrode and insulating means therefor mounted in said shell and terminating intermediate the ends of said barrel, and an ignition coil unit slidably mounted in said barrel, said unit comprising a rigid insulating member having an axial recess in one end thereof for receiving the end of said assembly, a core magnetic material in said recess, primary yand secondary windings on said insulating member, a terminal in the end of said insulating member opposite said recess, means connecting said primary Winding to said terminal and means including resilient means for connecting said secondary winding to said electrode when said unit is inserted in said barrel.

3. In ignition apparatus of the class described, a tubular shell having a tubular shielding barrel extending therefrom, a center electrode assembly including a center electrode and insulating means therefor mounted in said shell and terminating intermediate the ends of said barrel, and an ignition coil unit in said barrel, said unit comprising a rigid insulating member having an axial recess in one end thereof for receiving the end of said assembly, a core of magnetic material in said recess, primary and secondary windings wound on said insulating member, a split sleeve of magnetic material surrounding said windings, an insulating layer surrounding said split sleeve and means for operatively connecting the high potential end of said secondary winding to said electrode.

4. In ignition apparatus of the class described, a tubular shell having a tubular shielding barrel extending therefrom, a center electrode assembly including a center electrode and insulating means therefor mounted. in said shell and terminating intermediate the ends of said barrel, and a transformer coil unit adapted to be slidably inserted into said barrel, said coil unit comprising a rigid insulating member having an axial recess in one CTI end thereof for receiving the end of said assembly,1a core of magnetic material in said recess,`

electrically conductive resilient means interposed between said core and said electrode, primary and secondary windings on said insulating member, a

sleeve of magnetic material around said windings, insulating means between said sleeve and said barrel, means electrically connecting said secondary winding and said resilient means,` a- Aterminal in the end of said insulating member opposite said recess and means connecting said primary winding to said terminal.

5.- An ignitionl unit comprising a spark plug of thetype wherein a shielding barrel surrounds v and-extends beyond an insulated center electrode,

ignition coil unit in said barrel comprising a rigid insulating member having a recess therein for receiving the end of said insulated electrode, primary and secondary windings on said insulating member, a metallic core in said recess, and means for operatively connecting the high potential end of said secondary winding to said electrode.

'7. An ignition coil unit comprising a spark plug of the type wherein a shielding barrel surrounds and extends beyond a center electrode assembly including a center electrode and insulating means therefor, and an ignition coil in said barrel comprising primary and secondary windings wound on a rigid insulating member having a recess in one end thereof for receiving the end of said assembly, a terminal in the end of said member opposite said recess, means connecting the primary winding to said terminal and means for connecting the high potential end of said secondary winding to said electrode.

3. In -an ignition coil unit, a spark plug of the type wherein a tubular shielding barrel surrounds and extends beyond a center electrode assembly comprising a center electrode and insulating means therefor, and an ignition coil in said barrel comprising a rigid insulating member surrounding the end of said assembly, a core of magnetic material in said member, primary and secondary windings wound on said member, a split sleeve of magnetic material around said windings and insulating means interposed between said sleeve and said barrel.

9. An ignition coil unit comprising a rigid insulating member having external flanges at opposite ends thereof and a recess in one end thereor", a core of magnetic material in said recess, primary and secondary windings wound on said member between said flanges, a split sleeve of magnetic material surrounding said windings, insulating means around said sleeve, a terminal in the end of said member opposite said recess, means connecting said primary winding to said terminal, and means extending through the wall of said recess for connecting said secondary winding to said core.

10. An ignition coil unit comprising a rigid insulating member having a recess in one end thereof, a terminal in the other end of said member, a, core of magnetic material in said recess, primary and secondary windings wound on said member, means connecting said primary winding to; said. terminal, andineangs connecting; thehih,

potential? end of said secondary Winding, to SaidV core. Y

1,1. An ignition unitV ccnnprisingl av spark plug;

ofthe type wherein a shielding, barrel surroinnzsl and extends beyond a center electrodeassembly v including tubular insulating mean-s, andmetalic conducting means in said insulating means, at..

least4 a portion ci said ccnductinghmeans convsisting;V or -magneticV metal,y an ignition coi-1. in saidbarrel comprisingl primary. and secondari@l windings wound on a rigid insulating member hai/ingna recess in one end thereof for; receiving theend'of said ,assembiy, and means connecting the high potential end, of saidsecondary Winding; l5'

to: said conducting means.

1-2. In ignition apparatus of the class described,y a Vtubular metallic shell, a, center electrode as: sernblyy including tubular insulatingv means and conducting means therein mounted in said shell and terminating intermediate the ends thereof,

a portionof said conducting, means in the end ofk saidassenibiy Withiny said shell consisting` ofi magnetic flux conducting metal, and anv ignition` coijl unit inA said shell comprising primary and. secondary windings surrounding said flux: coni-- ducting; portion vof said conducting` means.

13. A transformer comprising teiescopedtubular insulators, transformer windings.v aboutone.

of said insulators, and a transformer; corecomprsing armetallic sleeve between saidfin-sulators.

1li. An ignition unit comprising .telesconed tubularinsulators, electrically connectedL conductingy means Within said insulators constitute ing aftransformer core, and transformerK Winde ingsaearried, big.- one of.; said insulators and con-- nected to the high tension end@ ciu said; core.

15. An ignition unit comprisingV telescoped tubular insulators,v a. conducting; bodyv mounted within, each- Qf; said, insulators, said: bodies beingA electrically interconnected, and transformer winding-s carried, bycne of` said insulators; and.

encircling said, bodies.- whereby` said bodies tend,

tu act as; a core for,` the transformer coil;

16.. ignition unit comprising; telescoped.

tuhular. insulatorsrseparated, byv a1 sleeve; of con.- ducting'material; electrically connected; conduct ingj; means; withinsaidl insulators andi` connected.,

withsa-id sleeve. to. constitute, a transformen core and` a" conductor, and transormer; windings car` riad. byone: of said insulators.; and connected atethe. high. tension; end. to said core..

M QRGAN G. WEATHERLY REFERENCES; CITED The followingA references are ofrecord in'Y the file or this patent:Y

UNITED STATES PATENTS 

